These utils functions/variables will be useful in the threshold ts lib
eg for calculating staking bonus rewards.

In the future we should create a contract wrapper for each contract the
threshold lib integrates to keep the same interface. In some cases
multiple services need the same contract data like deployment block or
address. So to avoid duplicating the creation of each contract in each
service can create one contract instance and pass to the service in
constructor.

Move fetching the staking bonus rewards to the threshold lib. Also add a
function to the staking and pre service to fetch necessary events to
calculate rewards.

Move fetching the interim staking rewards to the threshold ts lib and
update hooks to use the services from threshold lib.

Rewards is a wrapper for all type of rewards in the threshold network.
Currently there are 2 types of rewards: staking bonus and interim
staking rewards. We should keep in mind that calculated reward from
interim rewards service may include the staking bonus reward.

We keep the abi for `ComulativeMerkleDrop` contract in the threshold ts
lib.